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Chihuahuan Desert
The Chihuahuan Desert is a desert, and an ecoregion designation, that straddles the U.S.-Mexico border in the central and northern portions of the Mexican Plateau, bordered on the west by the extensive Sierra Madre Occidental range, and overlaying northern portions of the east range, the Sierra Madre Oriental. On the U.S. side it occupies the valleys and basins of central and southern New Mexico, Texas west of the Pecos River and southeastern Arizona; south of the border, it covers the northern half of the Mexican state of Chihuahua, most of Coahuila, north-east portion of Durango, extreme northern portion of Zacatecas and small western portions of Nuevo León. It has an area of about . It is the third largest desert of the Western Hemisphere and is second largest in North America, after the Great Basin Desert. Geography The terrain mainly consists of basins broken by numerous small mountain ranges. Several larger mountain ranges include the Sierra Madre, the Sierra del Carmen, the Sacramento Mountains, the Sandia-Manzano Mountains, the Magdalena-San Mateo Mountains, the Chisos, the Guadalupe Mountains, and the Davis Mountains. These create "sky islands" of cooler, wetter, climates within the desert, and such elevated areas have both coniferous and broadleaf woodlands, and even forests along drainages and favored exposures. The Chihuahuan Desert is higher in elevation than the Sonoran Desert to the west, mostly varying from in altitude. As a result, it tends to have a slightly milder climate in the summer (though usually daytime June temperatures are in the range of ). Winter weather varies from relatively mild to quite cold depending on altitude and the ferocity of northerly winds. Precipitation is somewhat more abundant than most of the southern Great Basin, the Sonoran, and Mojave deserts, however it is still usually less than per year, with much of the rain falling during the "monsoon" of late summer. The mean annual precipitation for the Chihuahuan Desert is with a range of approximately . Nearly two-thirds of the arid zone stations have annual totals between .Chihuahuan Climate, Chihuahuan Desert Research Institute Snowfall is scant except at the higher elevation edges. The Chihuahuan Desert is an ecoregion that has received little exploration and study. Therefore, it has not been classified or had subdivisions applied to it, as has the Sonoran Desert to the west. There are a few urban areas within the desert: the largest is Ciudad Juárez with almost two million inhabitants, neighboring El Paso; then the city of Chihuahua and Torreón. Albuquerque, Las Cruces and Roswell in New Mexico are among the other significant cities in this ecoregion. Saltillo and Monterrey are located in the border of the Chihuahuan desert. According to the World Wide Fund for Nature, the Chihuahuan Desert may be the most biologically diverse desert in the world, whether measured on species richness or endemism, although the region has been heavily degraded over time. Many native species have been replaced with Creosote Bush. The Mexican Wolf, once abundant, has been extirpated. The main cause of degradation has been grazing. Flora Creosote Bush (Larrea tridentata) is the dominant plant species throughout the Chihuahuan Desert. The other species it is found with depends on factors such as the soil, altitude, and degree of slope. Creosote Bush, Viscid Acacia (Acacia neovernicosa), and Tarbush (Flourensia cernua) dominate the northern portion. Yucca and Opuntia species are abundant in the central third, while Arizona Rainbow Cactus (Echinocereus polyacanthus) and Mexican Fire-barrel Cactus (Ferocactus pilosus) inhabit the southernmost portion. Herbaceous plants, such as Blue Grama (Bouteloua gracilis), Gypsum Grama (B. breviseta), and Hairy Grama (B. hirsuta), are dominant near the Sierra Madre Occidental. Lechuguilla (Agave lechuguilla), Honey Mesquite (Prosopis glandulosa), Opuntia macrocentra and Echinocereus pectinatus are the dominant species in western Coahuila. Anacahuita (Cordia boissieri), Ocotillo (Fouquieria splendens), Lechuguilla, and Yucca filifera are the most common species in the southeastern part of the desert. Candelilla (Euphorbia antisyphilitica), Mimosa zygophylla, Acacia glandulifera and Lechuguilla are found in areas with well-draining, shallow soils. The shrubs found near the Sierra Madre Oriental are exclusively Lechuguilla, Guapilla (Hechtia glomerata), Queen Victoria's Agave (Agave victoriae-reginae), Sotol (Dasylirion spp.), and Barreta (Helietta parvifolia), while the well-developed herbaceous layer includes grasses, legumes and cacti. Grasslands comprise 20% of this desert and are often mosaics of shrubs and grasses. They include Purple Three-awn (Aristida purpurea), Black Grama (Bouteloua eriopoda), and Sideoats Grama (Bouteloua curtipendula). Early Spanish explorers reported encountering grasses that were "belly high to a horse;" most likely these were Big Alkali Sacaton (Sporobolus wrightii) and Tobosa (Pleuraphis mutica) bottomlands. File:Creosote Larrea tridentata.jpg|Young Creosote Bush (Larrea tridentata) File:VanHornTX 2008.jpg|Yucca, Creosote, and Mesquite typify the plants in the Chihuahuan Desert File:Agave lechuguilla habitus.jpg|Lechuguilla (Agave lechuguilla)—one of the indicator plants of the Chihuahuan Desert See also References External links *Chihuahuan Desert images at bioimages.vanderbilt.edu (slow modem version) *Pronatura Noreste in the Chihuahuan Desert *Small desert beetle found to engineer ecosystems EurekAlert! March 27, 2008 Category:Chihuahuan Desert Category:Deserts and xeric shrublands in the United States Category:Ecoregions of the United States Category:Deserts and xeric shrublands Category:Ecoregions of Mexico Category:Deserts of Mexico Category:Deserts of New Mexico Category:Deserts of Texas Category:Deserts of Arizona Category:Southwestern United States Category:Regions of Northern Mexico Category:Natural history of Chihuahua Category:Natural history of Coahuila Category:Natural history of Durango Category:Natural history of Zacatecas Category:Natural history of Nuevo León Category:Mexican Plateau Category:Deserts of North America